<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        function san() {
            var a = +prompt('请输入第一个值')
            var b = +prompt('请输入第二个值')
            var c = +prompt('请输入第三个值')
        
            var giao =[a,b,c]
            var max = giao[0]
            for (i =0; i < 3; i++) {
                if (max < giao[i+1]) {
                max = giao[i+1]
                }
            }
            alert(max)
            }
            san()

    </script>
</body>
</html>